Wales are likely to be without James Hook and Dan Lydiate until the knockout stage but Ryan Jones may be fit to face Namibia in New Plymouth next Monday, six weeks after he suffered a calf strain.

Wales need Jones because, with Lydiate wearing a protective boot after damaging ankle ligaments during Sunday's victory over Samoa, they only have three fit back-rowers, two of whom, the captain Sam Warburton and the No8 Toby Faletau, have played in the bruising encounters against South Africa and Samoa.

The full-back Hook left the field against Samoa with a shoulder injury, putting Lee Byrne in line to make his first appearance of the tournament against Namibia, a match that will see Wales make multiple changes with the final group match, against Fiji, in mind.

Hook is expected to be out of action for between two and three weeks but Wales are waiting for the result of a scan on Lydiate's right ankle before estimating when he will return. "It is not broken," said the flanker. "We are waiting to see how it settles down over the next couple of days."

The Wales defence coach, Shaun Edwards, said it is too early to say when Hook and Lydiate would return. "Dan's in a moon boot, but they put moon boots on everything these days. James is a bit easier to read because he's done his AC joint. We think it's a grade one or two."

Wales have given their players two days off. When they trailed Samoa 10-6 at the interval, they were in danger of missing out on the quarter-finals for the fourth time in six tournaments but drew on reserves built up during two gruelling training camps in Poland during July.

"We were cursing the coach when we were in Poland," said the second row Luke Charteris. "It was woeful and we were wondering what we were doing there. It was worth it because the camps gave us the means to compete for the full 80 minutes and have given us a great deal of confidence.

"We showed tremendous attitude and character against Samoa. We did not panic when we were behind and we were patient. We know, though, that to progress we have to become sharper. We need to be more accurate because we created chances without finishing them off. We have got to become more clinical."

Samoa have to win their final two matches, against Fiji and South Africa, to have a chance of progressing.